Simple UIButton subclass that can show a customizable loading message

LoadingButton.swift

//
//  LoadingButton.swift
//  LoadingButton
//
//  Created by Fernando Ortiz on 4/10/16.
//  Copyright © 2016 Fernando Martín Ortiz. All rights reserved.
//

import UIKit

/**
 Simple UIButton subclass that can show a customizable loading message
 
 There are two important methods here:
 
 - startLoading(): Starts the loading animation and shows the loading message
 - stopLoading(): Stops the loading animation and shows the normal title.
 
 And has some customizable properties that can be inspected from Interface builder:
 
 - loadingText: The custom message that is shown when the loading animation starts. Defaults to "Loading..."
 - loadingLabelFontName: The custom font name for the loading label. The default font is System font with size 15.0
 - loadingLabelFontSize: The custom font size for the loading label. The default font is System font with size 15.0
 - loadingLabelColor: The custom textColor for the loading label. Defaults to blue.
 
 */
class LoadingButton: UIButton {
    
    // MARK: - Views -
    lazy var activityIndicatorView: UIActivityIndicatorView = {
        let activityIndicator = UIActivityIndicatorView()
        return activityIndicator
    }()
    lazy var loadingLabel: UILabel = {
        let label = UILabel()
        return label
    }()
    lazy var loadingStackView: UIStackView = {
        let stackView = UIStackView()
        stackView.axis = .horizontal
        stackView.spacing = 5.0
        return stackView
    }()
    
    // MARK: - Attributes -
    
    /// The custom message that is shown when the loading animation starts. Defaults to "Loading..."
    @IBInspectable
    var loadingText: String = "Loading..." {
        didSet {
            configureIBProperties()
        }
    }
    
    /// The custom font name for the loading label. The default font is System font with size 15.0
    @IBInspectable
    var loadingLabelFontName: String? = nil {
        didSet {
            configureIBProperties()
        }
    }
    
    /// The custom font size for the loading label. The default font is System font with size 15.0
    @IBInspectable
    var loadingLabelFontSize: CGFloat = 15.0 {
        didSet {
            configureIBProperties()
        }
    }
    
    /// The custom textColor for the loading label. Defaults to blue.
    @IBInspectable
    var loadingLabelColor: UIColor = UIColor.blue {
        didSet {
            configureIBProperties()
        }
    }
    
    private var lastTitle: String? = nil
    private lazy var defaultFont: UIFont = {
        let font = UIFont.systemFont(ofSize: 15.0)
        return font
    }()
    
    
    // MARK: - Init -
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    private func commonInit() {
        loadingStackView.addArrangedSubview(activityIndicatorView)
        loadingStackView.addArrangedSubview(loadingLabel)
        
        addSubview(loadingStackView)
        
        loadingStackView.translatesAutoresizingMaskIntoConstraints = false
        
        loadingStackView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
        loadingStackView.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
        
        loadingStackView.isHidden = true
        
        configureIBProperties()
    }
    
    // MARK: - Private configuration -
    private func configureIBProperties() {
        self.loadingLabel.text = loadingText
        self.loadingLabel.textColor = loadingLabelColor
        
        if let fontName = self.loadingLabelFontName {
            self.loadingLabel.font = UIFont(name: fontName, size: self.loadingLabelFontSize)
        } else {
            self.loadingLabel.font = self.defaultFont
        }
    }
    
    // MARK: - Public methods -
    
    /// Starts the loading animation and shows the loading message
    func startLoading() {
        if lastTitle == nil {
            self.lastTitle = self.titleLabel?.text
        }
        
        self.setTitle("", for: .normal)
        self.loadingStackView.isHidden = false
        self.activityIndicatorView.startAnimating()
    }
    /// Stops the loading animation and shows the normal title.
    func stopLoading() {
        self.setTitle(self.lastTitle, for: .normal)
        self.lastTitle = nil
        self.loadingStackView.isHidden = true
        self.activityIndicatorView.stopAnimating()
    }
    
}